The present invention relates in general to new and useful improvements in the sealing of closure-like elements to the neck of containers, and more particularly, to a process of applying a top element to a container using hot melt material to form a liquid seal therebetween.
Containers of various designs for storing and dispensing of liquid materials have achieved large consumer acceptance for a variety of household products. Of particular interest are liquid dispensing containers for household products such as detergents, fabric softeners, synthetic bleaching agents and the like. Certain of these containers have incorporated a measuring cup which also functions as a closure for the container by being securable to a so-called dripless pouring spout. One such liquid dispensing container is known from Muckenfuhs et al., U.S. Pat. No. 4,696,416.
The container of Muckenfuhs et al. includes a collar from which there extends a pouring spout sealingly secured to a dispensing orifice on the container. The collar and pouring spout form a drain back partition with a drainhole to collect and return residual liquid to the container, as well as return of unused liquid from the measuring cup. The collar is formed from material harder than the container such that an annular sealing ring providing on the collar will slightly deform or cut into the softened material of the top surface of the container neck to create a liquid seal thereat. Despite this apparent creation of a liquid seal, it has been found that containers of this construction have a tendency to leak during transport from the container filling station to the consumer. The loss of a liquid seal is further aggravated by the frequent rough handling of these containers during shipment and stocking in warehouses and on shelves of retail establishments.
Hot melt material for use as gaskets and seals in container closures has gained acceptance in the past several years. These hot melt materials traditionally have been based upon either ethylene or vinyl acetate copolymer and/or a styrenic block copolymer. There is known from Couturier et al., U.S. Pat. No. 4,870,128, the forming of a gasket from hot melt material including a copolymer of ethylene and an olefinic carboxylic acid. The gasket is formed by applying the hot melt material in molten flowable form to the inner surface of a closure lid in the shape of a gasket or as a molten lump and then molded into the desired gasket shape with a molding die. These gasketed closure lids are subsequently aged for an extended period, for example, 24 to 48 hours at room temperature, before the closure lid is applied to the container.
The resulting closure lid and gasket combination have been found suitable for use as bottle caps, metal or plastic, large container closures, pail lids, drum lids and the like. Preferably, these gasketed closure lids are disclosed as having utility as carbonated soft drink closures or in food packs, especially those which are pasteurized during processing such as pickles, jellies and jams, and fruit drinks. Although these closure lids having hot melt material formed gaskets are suitable for a variety of containers, the formed gasket requires an aging period or, at the very least allowed sufficient time to solidify from its applied molten state, prior to application to a container to form a conventional compression type seal. These gasketed closure lids are therefore not suitable for creating an instantaneous liquid seal between a closure and container, and particularly, those which do not rely upon the presence of a compressive force with the gasket to achieve the liquid seal.
The application of hot melt material to form a seal between a container and a top element, wherein the seal is subjected to a high top loading of a nature wherein conventional gasket materials such as plastisols will unduly flow and result in leakage is known from Dezio et al., U.S. Pat. No. 4,756,857. Dezio et al. discloses a liquid container having a neck provided with an unthreaded cylindrical portion to which there is secured a top element. Hot melt material is applied by means of an extrusion apparatus in the form of a continuous band having a preselected pattern into an annular recess formed within the top element. The top element is then compressed onto the cylindrical portion such that the hot melt material is extruded around the cylindrical portion to function as a gasket and a support for the top element relative to the container neck. In a variation, the container neck is provided with a threaded cylindrical portion engageable with corresponding threads provided internally within the top element. The hot melt material is applied within the channel of the top element in a similar manner. Upon applying the top element to the container neck by rotation thereof to achieve cooperative threaded engagement, the hot melt material by virtue of the necessity of having to form both a gasket and support is not spread about the threaded cylindrical portion.
During application of the top element to the container neck in Dezio et al., the hot melt material is extruded into an annular region which is in fluid communication with the interior of the container. This results in possible contamination of the container contents by the hot melt material, as well as possible chemical attack of the hot melt material dependent upon the particular liquid stored within the container. In addition, Dezio et al. requires that the hot melt material be applied by means of a complicated extrusion apparatus upon positioning the top element in operative relationship therewith. This necessitates that the top element be subsequently advanced from the extrusion apparatus and manipulated into position for application to the container neck. Accordingly, one can appreciate that there is an unsolved need for providing a process of sealing a top element to a container using hot melt material which overcomes the above disadvantages from the presently known processes.